Decorative paper comprising a yellow cellulose-based substrate

ABSTRACT

A decorative paper which has the yellowing be inconspicuous even if the surface resin layer comprising the cross linked coating layer of the ionizing radiation curable resin is provided on the decorative paper is provided. The decorative paper of the present invention uses a yellow base paper colored yellow or a white base paper colored white, containing a cellulose based pulp  1  and a colorant  2 , as a colored base paper  3 , and a surface resin layer  4  is provided thereon. More preferably, a whole solid layer is laminated between the colored base paper and the surface resin layer, wherein the whole solid layer is a yellow whole solid layer comprising a yellow ink is provided in the case that the base paper is the yellow base paper, or a white whole solid layer comprising a white ink is provided in the case that the base paper is the white base paper. Moreover, a patterned ink layer is also provided below the surface resin layer in general.

TECHNICAL FIELD

The present invention relates to a decorative paper used for a buildinginterior material (for example, a wall), a surface material of fittings(for example, a door) or furniture, or the like. In particular, itrelates to a decorative paper, capable of making the yellowing of thebase paper inconspicuous.

BACKGROUND ART

Conventionally, for a decorative paper used for a building interiormaterial (for example, a wall), a surface material of fittings (forexample, a door) or furniture, or the like, the surface properties suchas the wear resistance and the pollution resistance are required ingeneral. Therefore, for example, Japanese Patent Application Publication(JP-B) No. Sho 49-31033 discloses a decorative paper, which is producedin such manner that a patterned ink layer is formed by printing on abase paper, thereafter an ionizing radiation curable resin paint of anunsaturated polyester pre-polymer is applied on the surface to form acoating layer as the outermost surface layer, and then the coating layeris cross linked and cured by an electron beam to form a surface resinlayer.

In such case as described above of providing the decorative paper withthe surface resin layer as the outermost layer, which is formed by crosslinking a coating layer of an ionizing radiation curable resincomprising a monomer, a pre-polymer, or the like with the ionizingradiation such as an electron beam, a decorative paper having theexcellent surface physical properties such as the wear resistance andthe pollution resistance can be obtained owing to its high crosslinkage.

The decorative paper provided with the surface resin layer as a crosslinked coating layer of the ionizing radiation curable resin asmentioned above varies degree of cross linkage in the surface resinlayer affected by the ionizing radiation, but it involves the problem ofyellowing in any case nevertheless. In particular, the yellowing isconspicuous in the case of using the electron beam.

As to the reason for the yellowing, it was revealed that since thedecorative paper uses a paper made of a cellulose based pulp as the basematerial (base paper), if it is irradiated with the ionizing radiationfor cross linking and curing the surface resin layer, a radical (freeradical) is generated by the energy (quantum) of the ionizing radiation,and triggered thereby, scission of the principal chain of the cellulosemolecule is caused so as to produce a carboxyl group or a carbonyl groupso that these groups have the absorption spectra in the short wavelengthrange of the visible light band (“Influence of the electron beamradiation on the paper quality (second edition)/novel method forproviding the electron beam resistance to the paper”, Japan TappiJournal vol. 51, No. 6, published in June, 1997, page 945 to page 954).

Moreover, in the above-mentioned report, as the countermeasure for theyellowing, proposed is impregnation of the paper with an alcoholsolution of an electron beam reactive monomer such as a tetraethyleneglycol dimethacrylate (TEGDMA), a polyethylene glycol dimethacrylate(PEGDMA), or the like for allowing the monomer to scavenge the radicalgenerated at the time of the electron beam irradiation, and for crosslinking or graft polymerizing the monomer with a cellulose molecule atthe time of the electron beam irradiation.

This method is indeed one of the effective means for prevention of thebase paper yellowing at the time of the ionizing radiation irradiation.

However, since a special chemical is used for the impregnation, cost ofthe base paper becomes higher thus being problematic. Moreover, it iseffective for prevention of the yellowing, but not complete, and theyellowing can be conspicuous depending on amount of the electron beamirradiation, or depending on the kind of the design to be printed. Theyellowing becomes problematic particularly in the following two cases.

(1) The case that the design and appearance of the decorative paperinherently cannot tolerate the yellowing.

Examples include: the case of requiring a pure white appearance; thecase that the change of the hue itself becomes conspicuous by theyellowing such as pale blue, red, green, or the like; and the case thatthe base paper loses harmony with the patterned ink layer or the balanceof the color mixture by the yellowing so that the designed appearanceitself is changed.

(2) The case that the base paper yellowing itself can be tolerated, butchange of the hue before and after the ionizing radiation irradiationbecomes the obstacle in terms of the color tone administration of thedecorative paper.

For example, in general, a process of printing a patterned ink layer tothe base paper and a process of coating a surface resin layer andirradiating with an ionizing radiation are executed in differentprocessing machines. In this case, the patterned ink layer is printed byadministering the color tone so as to match the color tone with thestandard color immediately after the printing process. However, in thecase that the yellowing is generated by the ionizing radiation in thefollowing surface resin layer coating process, the once matched colortone becomes unmatched. Moreover, the degree of the yellowing generatesirregularity depending on the irregularity of the ionizing radiationirradiation condition, the irregularity of the base paper lot, theenvironmental humidity, or the like. Therefore, it is very difficultthat the color tone is matched preliminarily at the printing process soas to be matched with the standard color after having the yellowing atthe final process.

That is, an object of the present invention is to have the yellowing ofthe base paper by the ionizing radiation at the time of cross linkingthe coating layer inconspicuous even in the case that a decorative paperis designed to have a surface resin layer made of a cross linked coatinglayer of an ionizing radiation curable resin.

DISCLOSURE OF THE INVENTION

A decorative paper according to the present invention comprises a yellowbase paper which comprises a cellulose based pulp and a colorant and iscolored yellow and a surface resin layer which comprises a cross linkedcoating layer of an ionizing radiation curable resin, at least thesurface resin layer being laminated on the yellow base paper.

According to such design, the decorative paper of the present inventioncan have the yellowing inconspicuous, even if the surface resin layercomprising the cross linked coating layer of the ionizing radiationcurable resin is provided on the decorative paper and the base papercauses yellowing by the ionizing radiation at the time of cross linkingthe coating layer to be the surface resin layer, because the yellow basepaper which is colored yellow by the colorant from the beginning is usedas a base paper.

Moreover, in the above-mentioned design of the decorative paperaccording to the present invention, a yellow whole solid layercomprising a yellow ink is laminated between the yellow base paper andthe surface resin layer.

According to such design, since addition amount of the colorant in theyellow base paper can be reduced, the cost reduction and the preventionof the base paper strength deterioration due to the colorant additioncan be achieved. Furthermore, since the color tone of the coloring andthe degree of hiding can be ensured, the effect of having the yellowingof the base paper inconspicuous can further be improved. Moreover, theapplicability and the freedom can be improved in terms of the color toneof the decorative paper and the patterning design.

Alternatively, a decorative paper according to the present inventioncomprises a white base paper which comprises a cellulose based pulp andis colored white and a surface resin layer which comprises a crosslinked coating layer of an ionizing radiation curable resin, at leastthe surface resin layer being laminated on the white base paper.

According to such design, the decorative paper of the present inventioncan have the yellowing inconspicuous, even if the surface resin layercomprising the cross linked coating layer of the ionizing radiationcurable resin is provided on the decorative paper and the base papercauses yellowing by the ionizing radiation at the time of cross linkingthe coating layer to be the surface resin layer, because the white basepaper which is colored white by the colorant from the beginning is usedas a base paper so that the yellowing appears as if it is alleviated bylight scattering (degree of whiteness) owing to whiteness of the whitebase paper and the yellowing is also hidden by the hiding property ofthe white pigment. Furthermore, since the above-mentioned design in thedecorative paper of the present invention has the base paper in white(namely achromatic color), compared with the case of the base paper inyellow, it has no influence on the color tone of the printed pattern sothat it can cope with a pattern having any color tone, thus it isadvantageous in that it can be applied in the case of a pattern or adesign not allowing the yellowing.

Moreover, in the above-mentioned design of the decorative paperaccording to the present invention, a white whole solid layer comprisinga white ink is laminated between the white base paper and the surfaceresin layer.

According to such design, since addition amount of the colorant in thewhite base paper can be reduced, the cost reduction and the preventionof the base paper strength deterioration due to the colorant additioncan be achieved. Furthermore, since the color tone of the coloring andthe degree of hiding can be ensured, the effect of having the yellowingof the base paper inconspicuous can further be improved. Moreover, theapplicability and the freedom can be improved in terms of the color toneof the decorative paper and the patterning design.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view showing an example of an embodiment ofa decorative paper of the present invention.

FIG. 2 is a cross sectional view showing an example of anotherembodiment of a decorative paper of the present invention.

FIG. 3 is a cross sectional view showing an example of anotherembodiment of a decorative paper of the present invention.

FIG. 4 is a cross sectional view showing an example of anotherembodiment of a decorative paper of the present invention.

The numerals in the drawings denote the followings.

Cellulose based pulp (1); colorant (yellow colorant, white colorant)(2); colored base paper (yellow base paper, white base paper) (3);surface resin layer (4); whole solid layer (yellow whole solid layer,white whole solid layer) (5); patterned ink layer (6); decorative paper(S)

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, with reference to the drawings, embodiments of the presentinvention will be explained.

[Outline]

As illustrated by a decorative paper S in FIG. 1 showing the crosssectional view, a decorative paper according to the present inventionutilizes a yellow base paper or a white base paper as a colored basepaper 3 containing a cellulose based pulp 1 and a colorant 2, on which asurface resin layer 4 comprising a cross linked coating layer of anionizing radiation curable resin is provided. Then, more preferably, asillustrated by a decorative paper S in FIG. 2 showing the crosssectional view, the decorative paper is designed so as to dispose acolored whole solid layer 5 between the colored base paper 3 and thesurface resin layer 4. The color of the whole solid layer 5 is madepreferably yellow using a yellow ink in the case that the colored basepaper is a yellow base paper, and it is made preferably white using awhite ink in the case that the colored base paper is a white base paper.

Moreover, for the improvement of the design, in general, a patterned inklayer 6 is provided as in the decorative papers S illustrated in FIGS. 3and 4. The patterned ink layer 6 is disposed between the colored basepaper 3 and the surface resin layer 4. In the case that it is providedwith the whole solid layer 5, as shown in FIG. 4, it is disposed betweenthe whole solid layer 5 and the surface resin layer 4.

According to such design, even if the decorative paper of the presentinvention is provided with the surface resin layer comprising the crosslinked coating layer of the ionizing radiation curable resin and thebase paper causes yellowing when the coating layer is cross linked, theyellowing is allowed to be inconspicuous by the color of the base paperand the whole solid layer.

[Base Paper: Yellow Base Paper and White Base Paper]

IN the present invention, a yellow base paper or a white base paper isused as the base paper. The yellow base paper is a base paper containinga cellulose based pulp 1 and a colorant 2, and it colored in yellow. Incontrast, the white base paper is a base paper containing a cellulosebased pulp 1 and a colorant 2, and it is colored in white. According tothe decorative paper of the present invention, since such a colored basepaper is used, the yellowing of the cellulose based pulp (namely,transition of the hue into the yellow color) can be made inconspicuousat the time of irradiating with the ionizing radiation (it is remarkableparticularly in the case of an electron beam).

In the explanation of the present invention, both the yellow base paperand the white base paper may be generally referred to the colored basepaper 3.

As the cellulose based pulp 1 which is the material of the colored basepaper, any of a coniferous wood (N material) pulp, a broad leaf wood (Lmaterial) pulp, and a mixture thereof may be used. As the kind of thewood for the coniferous wood (N material) pulp, a silver fir, a Japanesered pine, a fir, a hemlock, a spruce, or the like can be presented. Asthe kind of the wood for the broad leaf wood (L material), an oak, abeech, a birch, a eucalyptus, or the like can be presented. Although theconiferous wood pulp is inferior to the broad leaf wood pulp in terms ofthe printing suitability and the formation evenness, however, it issuperior to the broad leaf wood pulp in terms of the pulp strength. Thebasis weight of the colored base paper is in general about 20 to 100g/M².

The white base paper is a base paper produced by adding a white colorantas the colorant 2 to a base paper so as to be whitened. The white basepaper alleviates the yellowing by the light scattering (degree ofwhiteness) due to whitened base paper itself, and it also hide theyellowing by the hiding property of the white colorant (white pigment).Since the white color is an achromatic color so as not to influence thecolor tone of the printed pattern on the surface, it is excellent interms of the capability of coping with a design of any color tone.

Moreover, as to a decorative paper which has a pattern or design nottolerating the yellowing, it is not possible to adopt the method ofcoloring the base paper in yellow, thus the method of whitening the basepaper is selected.

As the white colorant, it is preferable to select among known variouskinds of white colorants those not to be deteriorated and/or not to bediscolored by the ionizing radiation to be radiated. That is, aninorganic pigment is preferable as the white colorant. Specifically, onekind alone or a mixture of two more kinds of a titanium white, a leadwhite, an antimony white, a zinc white, a zinc sulfide, a lithopone anda basic lead sulfide can be used. In particular, the titanium white ismost preferable in terms of the degree of whiteness and the hidingproperty.

Moreover, although the white colorant can be used alone, it may be usedin combination with a colorant of another hue in a range notdeteriorating the effect of having the yellowing inconspicuous. That is,the white color in the present invention may be a slightly grayishwhite, a white color having a slight hue (for example, a white slightlyhaving a hue of pink, pale blue, pale green, pale yellow, or the like)in addition to the pure white.

The addition amount of the colorant in the white base paper can bedetermined to an appropriate amount depending on the effect of havingthe yellowing inconspicuous, the paper making suitability, the paperprinting and processing suitability and the adjustment with respect tothe cost, and it is in general about 5 to 15% by mass.

In contrast, the yellow base paper is a base paper in which the basepaper itself is colored in yellowed from the beginning by adding ayellow colorant as the colorant 2 to the base paper. The yellow basepaper has the above-mentioned yellowing inconspicuous owing to theyellowness of the base paper itself by having the yellowing generated bythe ionizing radiation irradiation be alleviated in the original yellowcolor of the yellow base paper.

As the yellow colorant, it is preferable to select among known variouskinds of yellow colorants those not to be deteriorated and/or not to bediscolored by the ionizing radiation to be radiated. Specifically, onekind alone or a mixture of two more kinds of an inorganic pigments suchas a yellow iron oxide, a yellow lead, a titanium yellow, a zinc yellow,a barium chromate and Chinese yellow, or the like, and an organicpigment such as an isoindolinone yellow, a bendizine yellow, a polyazoyellow, or the like can be used. In particular, in terms of theresistance to the ionizing radiation, the above-mentioned inorganicpigments are most preferable. Moreover, in the case of the yellow basepaper, as to the colorant to be added, although the yellow colorant canbe used alone, a colorant of another hue may be used in a combination ina range not deteriorating the effect of having the yellowinginconspicuous. That is, the yellow color in the present invention may bea yellow based color having the hue in the vicinity of the yellow color(for example, the color of a yellowish green, an orange, a yellowishbrown, or the like) in addition to the pure yellow.

As to the coloring degree of the yellow base paper, it is preferablethat the b value in the CIE 1976 (L*a*b*) color system is +6 or more. Asto the coloring degree of the yellow base paper, the density ispreferably made higher in order to have the yellowing accompanied by theionizing radiation irradiation of the cellulose be conspicuous, however,the density is preferably made lower as much as possible in order toprovide the applicability of the color tone and the patterning design ofthe decorative paper. By having the coloring degree of the yellow basepaper of +6 or more in the L*a*b* color system, the color differenceafter the ionizing radiation irradiation can be restrained to the halfor less compared with a base paper which is not colored, and therebyachieve no problematic level for practical use.

The addition amount of the colorant in the yellow base paper can bedetermined to an appropriate amount depending on the effect of havingthe yellowing inconspicuous, the papermaking suitability, the paperprinting and processing suitability and the adjustment with respect tothe cost, and it is in general about 5 to 15% by mass.

[Surface Resin Layer]

Next, the surface resin layer 4 is a layer to be the surface layer onthe uppermost surface of the decorative layer, and it comprises a crosslinked coating layer of an ionizing radiation curable resin. Since thesurface resin layer has the high cross linkage, a decorative paperhaving the excellent surface properties such as the wear resistance andthe pollution resistance can be obtained. The surface resin layer isformed as a colorless transparent layer in general.

The surface resin layer can be formed by coating a liquefied ionizingradiation curable resin (composition) by a known coating method such asgravure coating and roll coating, and cross linking the coating layer bythe ionizing radiation irradiation. The surface resin layer can also beformed by whole solid printing by gravure printing, or the like. Thethickness of the surface resin layer is about 1 to 30 g/m² (based on thesolid component) in general in terms of the coating amount.

As to the ionizing radiation curable resin, specifically, a compositioncapable of being cross linked and cured by the ionizing radiation, inwhich a pre-polymer (including the so-called oligomer) and/or a monomerhaving a radical polymerizable unsaturated bond or a cationpolymerizable functional group in the molecule are mixed with each otheras required can be preferably used. The ionizing radiation here denotesan electromagnetic wave or a charged particle having an energy capableof polymerizing and crosslinking molecules, and it is commonly anelectron beam (EB) or an ultraviolet ray (UV) in general. However,compared with the ultraviolet ray, the electron beam can easilygenerates the yellowing due to scission of the cellulose molecule in thebase paper. Since the object of the present invention is to have theyellowing inconspicuous, it is particularly preferable for the ionizingradiation curable resin to use a resin of the type utilizing theelectron beam for the cross linking.

The above-mentioned pre-polymer or monomer is specifically a compoundhaving a radical polymerizable unsaturated group such as a(meth)acryloyl group and a (meth)acryloyl oxy group, a cationpolymerizable functional group such as an epoxy group, or the like inthe molecule. The pre-polymer and the monomer can be used alone or as amixture of a plurality of kinds. Here, for example, the (meth)acryloylgroup denotes an acryloyl group or a methacryloyl group. Moreover, asthe ionizing radiation curable resin, a polyene/thiol based prepolymeras a combination of a polyene and a polythiol can be preferably used aswell.

As the examples of a pre-polymer having a radical polymerizableunsaturated group in the molecule, a polyester (meth)acrylate, aurethane (meth)acrylate, an epoxy (meth)acrylate, a melamine(meth)acrylate, a triazine (meth)acrylate, or the like can be presented.As to the molecular weight, those having about 250 to 100,000 can beused in general. The (meth) acrylate denotes an acrylate or amethacrylate.

As the examples of a monomer having a radical polymerizable unsaturatedgroup in the molecule, a monofunctional monomer such as a methyl (meth)acrylate, a 2-ethylhexyl (meth) acrylate, a phenoxy ethyl(meth)acrylate, or the like can be presented. Moreover, a polyfunctionalmonomer such as a diethylene glycol di (meth) acrylate, a propyleneglycol di(meth)acrylate, a trimethylol propane tri(meth)acrylate, atrimethylol propane ethylene oxide tri(meth)acrylate, adipentaerythritol tetra(meth)acrylate, a dipentaerythritolpenta(meth)acrylate, a dipentaerythritol hexa(meth)acrylate, or the likecan be presented.

As the examples of a pre-polymer having a cation polymerizablefunctional group in the molecule, an epoxy based resin such as abisphenol type epoxy resin, and a novolak type epoxy compound, apre-polymer of a vinyl ether based resin such as a fatty acid basedvinyl ether and an aromatic based vinyl ether can be presented.

As the thiol, a polythiol such as a trimethylol propane trithiglycolate,a pentaerythritol tetrathioglycolate can be presented. Moreover, as thepolyene, one produced by adding an allyl alcohol to both ends of apolyurethane of a diol and a diisocyanate can be presented.

In the case of cross linking by the ultraviolet ray, a photopolymerization initiating agent is added to the ionizing radiationcurable resin. In the case of a resin system having a radicalpolymerizable unsaturated group, as the photo polymerization initiatingagent, aceto phenones, benzo phenones, thioxantones, a benzoin, benzoinmethyl ethers can be used alone or as a mixture. Moreover, in the caseof a resin system having a cation polymerizable functional group, as thephoto polymerization initiating agent, an aromatic diazonium salt, anaromatic sulfonium salt, an aromatic iodonium salt, a methalocenecompound, a benzoin ester sulfonate, or the like can be used alone or asa mixture.

The addition amount of these photo polymerization initiating agents isabout 0.1 to 10 parts by mass with respect to 100 parts by mass of theionizing radiation curable resin.

To the above-mentioned ionizing radiation curable resin, various kindsof additives may further be added as needed. As the additives, there maybe exemplified; a thermoplastic resin such as a vinyl chloride-vinylacetate copolymer a vinyl acetate resin, an acrylic resin, and acellulose based resin; an extender (filler) comprising fine particles ofa calcium carbonate, a barium sulfate, an antifriction agent to bedescribed later, or the like; a lubricating agent such as a siliconeresin and a wax; a colorant such as a dye and a pigment, or the like.

The antifriction agent may be added as needed in order to furtherimprove the wear resistance. As the antifriction agent, inorganicparticles harder than the cross linked coating layer of the ionizingradiation curable resin can be used. As the material for the inorganicparticles, an alumina (α-alumina, or the like), an alumino silicate, asilica, a glass, a silicon carbide, a boron nitride, a diamond, or thelike can be presented. The shape of the inorganic particles isspherical, polyhedron (cube, regular octahedron, other polyhedrons, orthe like), scale-like, amorphous, or the like. The average particle sizeof the inorganic particles is preferably about 3 to 30 μm. In the casethat the average particle size is too small, the wear resistanceimprovement effect is deteriorated, and in the case that it is toolarge, the surface flatness is lowered. The addition amount of theinorganic particles is about 5 to 30% by mass with respect to the totalamount of the resin component.

As the electron beam source for the ionizing radiation, various kind ofelectron beam accelerators such as a Cockcroft Walton type, a Van deGraaff type, a resonance potential transformer type, an insulation corepotential transformer type, a straight type, a dynamitron type and ahigh frequency type can be used, and those to radiate electrons havingan energy of 100 to 1,000 keV, preferably 200 to 300 keV are used.Moreover, as the ultraviolet ray source, light sources such as an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a low pressuremercury lamp, a carbon arc lamp, a black light and a metal halide lampor the like can be used. As to the wavelength of the ultraviolet ray, ingeneral, a wavelength range of 190 to 380 nm is used mainly.

[Whole Solid Layer]

In addition to coloring of the base paper, in the case that a patternedink layer is further present between the base paper and the surfaceresin layer, it is preferable to form a white whole solid layer made ofa white ink or a yellow whole solid layer made of a yellow ink, as thewhole solid layer 5, between the base paper and the patterned ink layerin viewpoint of the effect of having the yellowing inconspicuous. Thatis, the combination use of the colored base paper 3 with the whole solidlayer 5 has the following advantages (1) and (2). In the explanation ofthe present invention, the white whole solid layer and the yellow wholesolid layer may both be referred to as the whole solid layer.

As the white colorant in the above-mentioned white ink, the whitecolorants described for the above-mentioned white base paper can beused. Moreover, as the yellow colorant in the above-mentioned yellowink, the yellow colorants described for the above-mentioned yellow basepaper can be used. That is, at least a white colorant is added to thewhite whole solid layer, and at least a yellow colorant is added to theyellow whole solid layer. Moreover, as the binder resin for theabove-mentioned white ink and yellow ink, known resin to be describedlater for the patterned ink layer can be used as needed.

The whole solid layer can be formed by whole solid printing using ayellow or white ink by a coating method such as gravure coating, rollcoating, or the like or a printing method such as gravure printing orthe like. The thickness of the whole solid layer is generally about 1 to10 g/m² (based on the solid component) in terms of the coating amount.

The reasons why the whole solid layer is provided are as follows.

(1) Reduction of addition amount of the colorant in the base paper. Thatis, in the case that the colorant is added only to the base paper, thecolorant is naturally distributed to the entirety in the thicknessdirection of the base paper. Then, since the thickness of the base paperis thick (about 100 μm in general), the total addition amount of thecolorant finally becomes large. As a result, there may be easily causedproblems such that: paper dusts is liable to generate at the time ofprocessing; the cost gets higher; or furthermore, the strength of thebase paper is deteriorated and the decorative paper is thereby liable torupture at the time of post processing such as a process to fixing thedecorative paper.

In contrast, in the case that the base paper is to be colored inappearance only by the whole solid layer without adding a colorant inthe base paper, since the whole solid layer as the ink layer is thin(about 1 to 10 μm in general), if the colorant is added by an amountsufficient for having the yellowing of the base paper inconspicuous, theink flowability and the printing suitability are deteriorated. Moreover,if the ink flowability and the printing suitability are ensured, thecoloring and hiding effect becomes insufficient.

On the other hand, in the case that a colorant is added into the basepaper and a whole solid layer also including a colorant is formed(laminated) on a surface of the base paper, since the addition amount inthe colorant to the base paper can be reduced, cost down, prevention ofthe base paper strength deterioration and prevention of the paper dustgeneration can be achieved. Furthermore, the color tone of the coloringand the hiding degree can be ensured so that the effect of having theyellowing of the base paper inconspicuous can be sufficient.

(2) Improvement of the color tone of the base paper, the applicabilityand the freedom of the patterning design. That is, in the case that thecolorant is added only to the base paper, a part of the pattern or thedesign depends on the color tone of the base paper. Therefore, thelimitation to the pattern or the design by the color tone of the basepaper becomes strict. Moreover, the base paper is generally made througha large lot process so that it is difficult to deal with production oflarge number of kinds by small lots. Therefore, it is practicallydifficult to finely adjust the color tone of the base paper.

On the other hand, in the case that a colorant is added into the basepaper and a whole solid layer also including a colorant is formed(laminated) on a surface of the base paper, it is easy to finely adjustthe color tone of the whole solid layer at the time of printing evenwhen using one kind of a base paper, and thereby the freedom of thepatterning design of the decorative paper can be widened. However, sincethe original purpose of the color tone fine adjustment of the wholesolid layer is to having the yellowing of the base paper inconspicuous,the color tone of the whole solid layer is not to depart from the whitebase or yellow base.

The embodiments of the whole solid layer are as the following (A) to(D). In viewpoint of the original purpose of the present invention ofrealizing the above-mentioned advantages by the associative effect ofthe colored base paper and the whole solid layer, the embodiments (A)and (B) are most preferable. The positional relationship of the layersin the case of providing the patterned ink layer is shown at the sametime.

(A) White base paper/white whole solid layer/(patterned inklayer)/surface resin layer

(B) Yellow base paper/yellow whole solid layer/(patterned inklayer)/surface resin layer

(C) White base paper/yellow whole solid layer/(patterned inklayer)/surface resin layer

(D) Yellow base paper/white whole solid layer/(patterned inklayer)/surface resin layer

[Outline of the Other Constituent Layers]

According to the decorative paper of the present invention, in additionto the above-mentioned colored base paper, the surface resin layer, orfurthermore, the whole solid layer, conventionally known other layersmay optionally be provided, as needed. For example, a patterned inklayer frequently used in general can be presented. In addition thereto,a sealer layer, a primer layer, or the like can be presented.

In a case that the whole solid layer 5 is present upon providing thepatterned ink layer 6, the patterned ink layer 6 is naturally providedbetween the whole solid layer 5 and the surface resin layer 4 (see FIG.4). Moreover, although it is not shown in the figure, the laminationpositional relationship with respect to the other layers such as asealer layer and a primer layer generally meets the followingrelationship (a) or (b). Also here, the positional relationship of thelayers in the case of providing the patterned ink layer is shown at thesame time.

(a) Colored base paper/sealer layer/whole solid layer/(patterned inklayer)/primer layer/surface resin layer

(b) Colored base paper/whole solid layer/sealer layer/(patterned inklayer)/primer layer/surface resin layer

[Patterned Ink Layer]

The patterned ink layer 6 is a layer for expressing a patterning design,or the like. It is provided in general, however, it may be omitted whennot needed. Moreover, in the case of providing the patterned ink layer,the content of the patterned ink layer such as a forming method, amaterial, a design or the like for the patterned ink layer is notparticularly limited. The patterned ink layer is generally formed usingan ink by a conventionally known printing method such as gravureprinting, silk screen printing, offset printing, gravure offsetprinting, ink jet printing, or the like.

The patterning design is for example, a wood pattern, a stone pattern, asand pattern, a cloth pattern, a tile like pattern, a brick likepattern, a leather pattern, characters, marks, a geographic pattern, acombination of two kinds of more among them, or the like.

The ink used for forming the patterned ink layer is made of: a vehiclecomprising a binder or the like; a colorant such as a pigment and a dye;and additives to be added optionally thereto such as an extender, astabilizing agent, a plasticizing agent, a catalyst, a curing agent orthe like. The binder resin may be optionally selected out of athermoplastic resin, a thermosetting resin, an ionizing radiationcurable resin or the like according to requirement such as the physicalproperty, the printing suitability or the like. For example, a soleresin or a mixture resin containing these resin is used as a binderresin by selecting among followings: a cellulose based resin such as anitro cellulose, a cellulose acetate and a cellulose acetate propionate;an acrylic resin such as a polymethyl (meth)acrylate, a polybutyl(meth)acrylate and a methyl (meth)acrylate-butyl(meth)acrylate-2-hydroxy ethyl (meth)acrylate copolymer; a urethaneresin; a vinyl chloride-vinyl acetate copolymer; a polyester resin; analkyd resin, or the like can be used for the binder resin. Moreover, asthe colorant, an inorganic pigment such as a titanium white, a carbonblack, an iron black, an iron red oxide, a yellow lead and aultramarine, an organic pigment such as an aniline black, a quinacridoneread, an isoindolinone yellow and a phthalocyanine blue, a brightpigment such as a titanium dioxide covered mica, an aluminum or anotherfoil or the like, and other dyes.

[Sealer Layer]

The sealer layer is formed by coating a liquefied resin composition bygravure coating, roll coating or the like and solidifying the coatinglayer. Moreover, the sealer layer may be formed by whole solid printingby gravure printing or the like. The coating amount is about 0.5 to 10g/m² (based on the solid component), and the base paper is impregnatedwith at least a part of the resin composition.

The sealer layer is formed in order to prevent the phenomenon that aliquefied surface resin layer which is coated and not cured yet isreduced in film thickness due to the absorption of the liquefied surfaceresin layer into the inside of the base paper, or that the formationirregularity of the base paper results in the gross irregularity of thecoating layer. Moreover, the sealer layer is formed for improving theabrasion resistance by reinforcing the adhesion between the patternedink layer and the surface resin layer.

As the material of the sealer layer, one kind or a mixture of two ormore kinds of a urethane resin, an acrylic resin, a polyvinyl butylal,an epoxy resin, an amino alkyd resin or the like can be used.

As the above-mentioned urethane resin, a two liquid curing type urethaneresin, an one liquid curing type (dampness curing type) urethane resin,a thermoplastic urethane resin or the like can be used.

The two liquid curing type urethane resin is an urethane resincontaining a polyol as the main ingredient and an isocyanate as acrosslinking agent (curing agent). As the polyol, those having two or morehydroxyl group in a molecule, for example, a polyethylene glycol, apolypropyleneglycol, an acrylicpolyol, a polyesterpolyol, a polyetherpolyol, a polycarbonate polyol, a polyurethane polyol or the like can beused. Moreover, as the isocyanate, a polyvaleic isocyanate having two ormore isocyanate groups in a molecule can be sued. For example, anaromatic isocyanate such as a 2, 4-trilene diisocyanate, a xylenediisocyanate, a 4,4′-diphenyl methane diisocyanate, or an aliphatic (oralicyclic) isocyanate such as a 1,6-hexamethylene diisocyanate, anisophorone diisocyanate, a hydrogenated trilene diisocyanate, and ahydrogenated diphenyl methane diisocyanate can be used. Alternatively,an addact products or a polymer of the above-mentioned kinds ofisocyanates can be used as well. For example, an addact of a trilenediisocyanate, a trimer of a trilene diisocyanate or the like can bepresented.

In the above-mentioned isocyanates, the aliphatic (or alicyclic)isocyanates are preferable in viewpoint of enhancing the weatherresistance and the resistance to thermal yellowing. Specifically, forexample, a hexamethylene diisocyanate can be presented.

On the other hand, the one liquid curing type urethane resin is acomposition containing, as the essential component, a prepolymer havingan isocyanate group on the molecule end. Generally, the above-mentionedprepolymer is a prepolymer having one or more isocyanate group on bothends of the molecule. Specifically, it is a polyisocyanate prepolymerhaving a skeleton such as a polycarbonate skeleton, a polyurethaneskeleton, a polybutadiene skeleton, a polyester skeleton or the like.The isocyanate groups react with each other by the moisture content inthe air so as to generate the chain prolonging reaction. As a result, areaction product having an urea bond in a molecule chain is generated.The isocyanate groups on the molecule ends further react with the ureabond so as to generate a biuret reaction and be branched or grafted togenerate a cross linking reaction.

Moreover, as the above-mentioned acrylic resin, an acrylic resin such asa polymethyl (meth)acrylate, a polyethyl (meth)acrylate, a polybutyl(meth)acrylate, a methyl (meth)acrylate-butyl (meth)acrylate copolymer,a methyl (meth)acrylate-styrene copolymer, a methyl (meth)acrylate-butyl(meth)acrylate-(meth)acrylic acid-2-hydroxy ethyl copolymer, a methyl(meth)acrylate-butyl (meth)acrylate-(meth)acrylic acid-2-hydroxyethyl-styrene copolymer or the like can be presented [here, the term“(meth)acrylic” is used for the meaning of acrylic or methacrylic.].

[Primer Layer]

The primer layer is formed by liquefying a resin composition by methodof dissolving or the like, coating it by gravure coating, roll coating,or the like, and then solidifying the coating layer. Also, the primerlayer may be formed by whole solid printing by gravure printing or thelike. The purpose of the primer layer is to alleviate the shear stressgenerated in the interface between the surface resin layer and thepatterned ink layer due to the curing and contraction upon forming thesurface resin layer, and furthermore, to reinforce the adhesion betweenthe surface resin layer and the patterned ink layer by the chemicaladhesion. Moreover, as a result, the abrasion resistance can further beimproved. The coating amount is about 0.1 to 5 g/m² (based on the solidcomponent).

As the resin used for the primer layer, one kind or a mixture of two ormore kinds of a urethane resin, an acrylic resin, a polyvinyl butylal orthe like can be used. As the urethane resin and the acrylic resin, theresins listed for the above-mentioned sealer layer or the like can beused.

[Base Material to Be Bonded]

The decorative paper of the present invention can be used as a surfacedecorative material by being fixed on the surface of various basematerial to be bonded.

The above-mentioned base material to be bonded is not particularlylimited. For example, the material of the base material to be bonded maybe inorganic non metal based, metal based, wood based, plastic based orthe like. Specifically, as to the inorganic non metal based ones, forexample, a non pottery ceramic industry based material such as amanufactured cement, an extrusion cement, a slug cement, an ALC (lightweight bubble concrete), a GRC (glass fiber reinforced concrete), a pulpcement, a wood chip cement, an asbestos cement and a calcium silicate,and an inorganic material such as an earthen ware, a pottery, aporcelain, a stone ware, a glass, a ceramic such as a porcelain enamel,or the like can be presented. Moreover, as to the metal based ones, forexample, a metal material such as an iron, an aluminum and a copper canbe presented. Moreover, as to the wood based ones, for example, a singleplate, a plywood, a particle board, a fiber board, an integratedmaterial, or the like made of a Japanese cryptmeria, a Japanese cypress,an oak, a lauan, a teak, or the like can be presented. Moreover, as tothe plastic based ones, for example, a resin material such as apolypropylene, an ABS resin and a phenol resin can be presented.

The shape of the base material to be bonded may be optional such as aflat plate, a curved plate and a polygonal pillar.

[Application]

Moreover, although the application of the decorative paper of thepresent invention is not particularly limited, for example, it can beused by being fixed on the surface of the base material to be bonded asmentioned above so as to serve as a building interior material such as awall, a ceiling or the like, a surface material for fittings such as adoor, a door frame, a window frame or the like, a surface material for afixture member such as a round rim a base board or the like, a surfacematerial for a furniture such as a chest of drawers and a cabinet or thelike.

EXAMPLES

Hereinafter, the present invention will be explained in further detailswith reference to the examples.

Example 1

A decorative paper whose design comprises a white base paper/a sealerlayer/a patterned ink layer/a surface resin layer was produced asfollows.

First, as the white base paper to be the colored base paper, a basepaper of an acrylic resin latex impregnated paper of a 50 g/m² basicweight, which uses a cellulose based pulp made of an L material andcontains a white pigment, as the colorant, made of a titanium white at12% by mass with respect to the entire base paper was prepared.

Then, a sealer layer was formed on a surface to be the front side of theabove-mentioned colored base paper by coating a coating liquid of a twoliquid curing type urethane resin comprising 100 parts by mass of apolyester polyol and 8 parts by mass of a 1,6-hexamethylene diisocyanateon the entirety of the base paper by a gravure roll coating method so asto have 5 g/m² of coating amount (based on the solid component).

Next, a patterned ink layer expressing a grain design of a Japanesecryptmeria was formed on the sealer layer by gravure printing with theuse of an ink comprising a nitro cellulose based resin as the binderresin and a color pigment as a colorant mainly composed of a carbonblack and an iron red oxide.

Next, a coating layer having a 10 μm thickness was formed over theabove-mentioned patterned ink layer by coating an electron beam curingtype ionizing radiation resin coating liquid having the below-mentionedcomposition on the entirety of the base paper by a roll coating method.Then, the coating layer was irradiated with an electron beam in theirradiation condition of 175 keV, 50 kGy (5 Mrad) using a scanning typeelectron beam radiating device, so that the coating layer was crosslinked and cured to form a colorless transparent surface resin layerformed of a cross linked coating layer, thus obtaining a desireddecorative paper.

Ionizing radiation curable resin paint Trifunctional polyester acrylateprepolymer 60 parts by mass Trimethylol propane triacrylate 10 parts bymass 1,6-hexane diol diacrylate 29 parts by mass Silicone acrylate  1part by mass

The processes of the sealer layer formation, the patterned ink layerformation, the surface resin layer coating and electron beamirradiation, or the like and the color tone evaluation to be describedlater were all executed in the atmosphere of 23° C. and 55% RH.

Example 2

A decorative paper whose design comprises a yellow base paper/a sealerlayer/a patterned ink layer/a surface resin layer was produced asfollows.

In the same manner as in the example 1 except that the yellow base paperwas used instead of the white base paper to be the colored base paper inthe example 1, the decorative paper was produced. As the above-mentionedyellow base paper, a base paper of an acrylic resin latex impregnatedpaper of a 50 g/m² basic weight, which uses a cellulose based pulp madeof an L material and contains a yellow pigment, as the colorant, made ofa yellow iron oxide at 12% by mass with respect to the entire base paperwas prepared.

Example 3

A decorative paper whose design comprises a white base paper/a whitewhole solid layer/a patterned ink layer/a surface resin layer wasproduced as follows (see FIG. 4).

In the same manner as in the example 1 except that the white whole solidlayer was formed instead of the sealer layer in the example 1, thedecorative paper was produced. The above-mentioned white whole solidlayer was formed by coating a white ink with a slight yellow brown tingewhich comprises a mixture of an acrylic resin and a nitro cellulosebased resin as the binder resin and the colorant mainly composed of atitanium white in combination use of a slight amount of a benzidineyellow on the entirety of the base paper by the gravure roll coatingmethod so as to have 4 g/m² of coating amount (based on the solidcomponent).

Example 4

A decorative paper whose design comprises a yellow base paper/a yellowwhole solid layer/a patterned ink layer/a surface resin layer wasproduced as follows (see FIG. 4).

The decorative paper was produced in the same manner as in the example 1except that: the yellow base paper was used instead of the white basepaper to be the colored base paper, which is a base paper of an acrylicresin latex impregnated paper of a 50 g/m² basic weight, using acellulose based pulp made of an L material and containing a yellowpigment, as the colorant, made of a yellow iron oxide at 12% by masswith respect to the entire base paper; and, the yellow whole solid layerwas formed instead of the sealer layer. The above-mentioned yellow wholesolid layer was formed by coating a yellow ink with a slight brown tingewhich comprises a mixture of an acrylic resin and a nitro cellulosebased resin as the binder resin and the colorant mainly composed of ayellow lead in combination use with an iron oxide read on the entiretyof the base paper by the gravure roll coating method so as to have 4g/m² of coating amount (based on the solid component).

Comparative Example 1

A decorative paper whose design comprises an uncolored base paper/asealer layer/a patterned ink layer/a surface resin layer was produced asfollows.

In the same manner as in the example 1 except that the colorless basepaper without adding the titanium white as the colorant was used insteadof the colored base paper in the example 1, the decorative paper wasproduced.

Comparative Example 2

A decorative paper whose design comprises an uncolored base paper/awhite whole solid layer/a patterned ink layer/a surface resin layer wasproduced as follows.

In the same manner as in the example 3 except that the colorless basepaper without adding the titanium white as the colorant was used insteadof the colored base paper in the example 3, the decorative paper wasproduced.

Comparative Example 3

A decorative paper whose design comprises an uncolored base paper/ayellow whole solid layer/a patterned ink layer/a surface resin layer wasproduced as follows.

In the same manner as in the example 4 except that the colorless basepaper without adding the yellow iron oxide as the colorant was usedinstead of the colored base paper in the example 4, the decorative paperwas produced.

[Performance Evaluation]

For the examples and the comparative examples, test pieces beforecoating the surface resin layer and after coating the surface resinlayer and irradiating with the electron beam were arranged side by sidefor the comparison, and the color tone difference thereof were confirmedby the visual observation. The test pieces were compared and evaluated 1minute after the electron beam irradiation. Moreover, the atmospherecondition at the time of the evaluation was 23° C. and 55% RH which wassame as in the production processes.

TABLE 1 Performance evaluation result Color examination Test piece(Evaluation by visual observation) Example 1 Difference unrecognizedExample 2 Difference unrecognized Example 3 Difference unrecognizedExample 4 Difference unrecognized Comparative The yellowing of the oneafter coating and example 1 irradiation was observed compared with theone before coating. Comparative The yellowing of the one after coatingand example 2 irradiation was observed compared with the one beforecoating. However, the degree of the yellowing was slight compared withthe comparative example 1. Comparative The yellowing of the one aftercoating and example 3 irradiation was observed compared with the onebefore coating. However, the degree of the yellowing was slight comparedwith the comparative example 1.

As shown in the table 1, although the color tone difference wasunrecognizable in the examples 1 to 4 so that the yellowing was notconspicuous, the yellowing was observed in those after coating andirradiating with the electron beam compared with those before coatingthe surface resin layer in the comparative examples 1 to 3.

INDUSTRIAL APPLICABILITY

(1) According to the decorative paper of the present invention, in theembodiment using a yellow base paper as the base paper, even if thesurface resin layer comprising the cross linked coating layer of theionizing radiation curable resin is disposed on the decorative paper andthe base paper causes yellowing by the ionizing radiation at the time ofcross linking the coating layer to be the surface resin layer, theyellowing is assimilated with the original yellow color of the yellowbase paper so that the yellowing can be inconspicuous.

(2) Furthermore, in the case that, in addition to the yellow base paper,a yellow whole solid layer comprising a yellow ink is laminated betweenthe yellow base paper and the surface resin layer, addition amount ofthe colorant in the yellow base paper can be reduced, so that cost down,the prevention of the base paper strength deterioration due to thecolorant addition, and the prevention of the paper dust generation canbe achieved as well as ensuring the color tone of the coloring and thehiding degree. Moreover, the applicability and the freedom can beimproved in terms of the color tone of the decorative paper and thepatterning design.

(3) In contrast, according to the decorative paper using a white basepaper as the base paper in the embodiment of the present invention, thedecorative paper of the present invention can have the yellowinginconspicuous, even if the surface resin layer comprising the crosslinked coating layer of the ionizing radiation curable resin is providedon the decorative paper and the base paper causes yellowing by theionizing radiation at the time of cross linking the coating layer to bethe surface resin layer, because the white base paper which is coloredwhite by the colorant from the beginning is used as a base paper so thatthe yellowing appears as if it is alleviated by light scattering (degreeof whiteness) owing to whiteness of the white base paper and theyellowing is also hidden by the hiding property of the white pigment.Furthermore, the decorative paper of the present invention has the basepaper in white, compared with the case of the base paper in yellow, ithas no influence on the color tone of the printed pattern so that it cancope with a pattern having any color tone, thus it is advantageous inthat it can be applied in the case of a pattern or a design not allowingthe yellowing.

(4) Furthermore, in the case that, in addition to the white base paper,a white whole solid layer comprising a white ink is laminated betweenthe white base paper and the surface resin layer, addition amount of thecolorant in the white base paper can be reduced, so that cost down, theprevention of the base paper strength deterioration due to the colorantaddition, and the prevention of the paper dust generation can beachieved as well as ensuring the color tone of the coloring and thehiding degree. Moreover, the applicability and the freedom can beimproved in terms of the color tone of the decorative paper and thepatterning design.

1. A decorative paper comprising: a yellow base paper which comprises acellulose based pulp and a colorant and is colored yellow; a patternedink layer for expressing a patterning design; and a surface resin layerwhich comprises a cross linked coating layer of an ionizing radiationcurable resin, at least the surface resin layer being laminated on theyellow base paper so as to cover the patterned ink layer formed on theyellow base paper, wherein b value of the yellow base paper is +6 ormore.
 2. The decorative paper according to claim 1, wherein a yellowwhole solid layer comprising a yellow ink is laminated between theyellow base paper and the surface resin layer so that the patterned inklayer exists between the yellow whole solid layer and the surface resinlayer.
 3. The decorative paper according to claim 2, wherein the wholesolid layer has a thickness of from about 1 to about 10 μm.
 4. Thedecorative paper according to claim 1, wherein the colorant is selectedfrom a yellow iron oxide, a yellow lead, a titanium yellow, a zincyellow, a barium chromate and Chinese yellow, an isoindolinone yellow, abendizine yellow and a polyazo yellow.